Print traceback in case of exception

The text of the exception is pretty much useless alone,
this makes it print the entire traceback.

driver.py

@@ -207,6 +207,7 @@ def run_test(testname):
             print (colorize('Test passed', COLOR_GREEN))
             return True
     except Exception as inst:
+        traceback.print_exc(file=sys.stdout)
         print (inst)
         pass
     print (colorize('ERROR', COLOR_RED))